Many aircraft include an environmental control system to supply and distribute conditioned air to one or more cabins within the aircraft. In some aircraft, the environmental control system includes an inlet duct that receives air conditioned air from an air source and two or more distribution ducts that supply the conditioned air to the aircraft cabins. A regulator valve that is moveable between an open position and a closed position may be mounted on one of the distribution ducts and used to regulate flow through the system. In such instances, when the regulating valve is in the closed position, conditioned air is supplied to the aircraft cabins via only one of the outlet ducts. Conversely, when the valve is in the open position, conditioned air is supplied to the aircraft cabins via all of the distribution ducts. The position of the regulator valve may be controlled by a valve actuator that receives valve position commands from an external controller and, in response to the received commands, moves the regulator valve to the commanded position.
In order to minimize aircraft weight, the air distribution ducts in the above-described environmental control system may be constructed with thin walls, and of relatively lightweight materials such as, for example, a wrapped composite. It will thus be appreciated that in certain rare instances if the system were to experience a sudden increase in flow rate when the regulating valve is in the closed position, pressure on one side of the regulating valve suddenly increase. If this pressure is not relieved, it may exceed an acceptable level and adversely impact the structural integrity of the distribution ducts. Preferably, if such an event were to occur, the regulating valve would be commanded to the open position to allow air to flow through all of the distribution ducts. However, in the highly unlikely event the control system did not command the regulating valve to open, or the regulating valve did not open for some other reason, the pressure in the distribution ducts upstream of the regulating valve may increase to an unacceptable level.
To address the above-noted overpressure concern, a parallel duct system has been implemented into some aircraft. The parallel duct system includes a separate duct coupled to one of the existing distribution ducts in the environmental control system, and a relief valve mounted on the duct. When the pressure increases to an unacceptable level, the relief valve opens and directs air either overboard or to other sections of the aircraft. However, this system, too, may have disadvantages. Specifically, the parallel duct system includes additional components which may increase the weight and/or manufacturing cost of the aircraft.
Accordingly, there is a need for an environmental control system that maintains the structural integrity of the distribution ducts in the unlikely event of an unexpected airflow rate increase. In addition, there is a need for an environmental control system that is lightweight and relatively inexpensive to implement. The present invention addresses one or more of these needs.